I have been a fan of this franchise since Tales of Symphonia on the Gamecube. I never could find anyone who enjoyed those games to play with me in local co-op. It mostly had to do with having only one character on screen. This made for a tedious experience for the other players. Perhaps a lot of people coped with it but I always felt it held back the franchise. I know they would have to change a lot of their structure to make it work but I think it is worth it.

I would simply like to know if I am the only one who wants online co-op (with in-game voice chat) in future Tales of games.

I definitely think that co-op would be a good idea. I also fell in love with the symphonia series and did not have many who were willing to play with me. Also playing through the great stories with friends being able to talk about what was happening, AS it happened would be quite BADASS if i do say so myself